KR20190027686A - Photon detecting device - Google Patents

Abstract

The present invention relates to a photon detecting device with high efficiency of light detection. The photon detecting device comprises: a first light receiving unit outputting a first signal by receiving a gate signal; a second light receiving unit outputting a second signal by receiving the gate signal; and a determination unit determining whether photons are received based on the first signal from the first light receiving unit and the second signal from the second light receiving unit. The photons are incident on the first light receiving unit of the first and second light receiving units. A breakdown voltage of the second light receiving unit is larger than a breakdown voltage of the first light receiving unit.

Description

[0001] PHOTON DETECTING DEVICE [

The present invention relates to a photon detection apparatus, and more particularly to a photon detection apparatus having high photon detection efficiency.

With the development of information and communication technologies, including quantum cryptography, the importance of techniques for detecting weak optical signals at the single photon level has increased.

In a single photon detector (single photon detector) capable of detecting a weak optical signal such as a single photon, an Avalanche Photo Diode is mainly used as a light receiving element.

In a single photon detection apparatus in which the Avalanche photodiode operates in the Gager mode, when the avalanche signal generated from the avalanche photodiode is weak, it is buried in the electrostatic capacitive response signal of the avalanche photodiode, It is difficult to acquire (or detect) the signal only.

An object of the present invention is to provide a photon detection device that operates at a high speed and has high light detection efficiency.

According to an aspect of the present invention, there is provided a photon detection apparatus including a first photodetector receiving a gate signal and outputting a first signal; A second light receiving unit receiving the gate signal and outputting a second signal; And a determination unit determining whether a photon is received based on a first signal from the first light receiving unit and a second signal from the second light receiving unit; A photon is incident on the first light receiving portion of the first light receiving portion and the second light receiving portion; The breakdown voltage of the first light receiving section and the breakdown voltage of the second light receiving section are different.

And the breakdown voltage of the second light receiving portion is larger than the breakdown voltage of the first light receiving portion.

The breakdown voltage of the second light receiving portion is 0.1 V to 10 V greater than the breakdown voltage of the first light receiving portion.

The first light-receiving unit and the second light-receiving unit may be configured with individual modules selected.

And the first light receiving portion and the second light receiving portion may be attached to the same submount with individual chips selected therefrom.

 The first light receiving portion and the second light receiving portion may be simultaneously fabricated on the same substrate.

The amplification layer of the first light receiving portion and the amplification layer of the second light receiving portion formed on the same substrate have different thicknesses.

The amplification layer of the second light receiving portion formed on the same substrate has a larger thickness than the amplification layer of the first light receiving portion.

And the amplification layer of the second light receiving portion formed on the same substrate has a thickness 5% to 50% larger than the amplification layer of the first light receiving portion.

The amplification layer of the first light receiving section and the amplification layer of the second light receiving section formed on the same substrate have different diameters.

And the amplification layer of the second light receiving portion formed on the same substrate has a larger diameter than the amplification layer of the first light receiving portion.

The photon detection apparatus further includes a substrate on which the first light receiving section and the second light receiving section are located.

The first light receiving portion and the second light receiving portion are located on the first surface of the substrate.

The photon detection device further includes a blocking film located on a second side of the substrate facing the first side of the substrate.

The blocking film has a through hole located corresponding to the first light receiving portion.

The photon detection device further includes an antireflection film disposed in the transmission hole.

Wherein the first surface of the substrate includes a first region and a second region separated by an element isolation groove between the first light receiving portion and the second light receiving portion; The first light receiving portion is located in the first region, and the second light receiving portion is located in the second region.

The electrostatic capacitive response characteristic of the first light receiving portion due to the gate signal is greatly different from the electrostatic capacitive response characteristic of the second light receiving portion due to the gate signal.

At least one of the first light receiving portion and the second light receiving portion includes an avalanche photo diode.

The photon detection apparatus according to the present invention provides the following effects.

First, the second light receiving portion of the present invention has a larger breakdown voltage than the first light receiving portion where light or photon is incident. Therefore, for the gate signal of the same size, the first light receiving section operates in the Geiger mode, while the second light receiving section does not operate in the Geiger mode. That is, since the second light receiving portion is operated in a reverse bias state which is smaller than the reverse bias state in the Geiger mode, the amplification of the second light receiving portion is small. Thus, the probability of occurrence of the dark-field intensity of the second light-receiving portion is reduced, thereby reducing the noise pulse from the second light-receiving portion, and consequently the reliability of the first light-receiving portion output affected by the noise pulse can be improved.

Secondly, since the noise pulse of the second light receiving portion is reduced, the first light receiving portion and the second light receiving portion can be manufactured on one same substrate. Therefore, the characteristics of the first light receiving portion and the characteristics of the second light receiving portion can be substantially maintained. That is, the characteristic deviation between the first light receiving portion and the second light receiving portion can be minimized.

Thirdly, as the noise pulse of the second light receiving portion is reduced, a more accurate size and shape of the capacitive response signal can be detected from the second light receiving portion.

Fourth, since the electrostatic capacitive response signal of the first light receiving portion and the electrostatic capacitive response signal of the second light receiving portion have substantially the same characteristics, the avalanche signal generated by the small avalanche amplification can be accurately detected.

Fifth, since the digital signal can be detected even if the amplification of the avalanche of the first light receiving unit is reduced, the after-pulse noise can be reduced.

1 is a diagram illustrating a photon detection apparatus according to an embodiment of the present invention.
2 is a view showing a waveform of a gate signal outputted from the gate signal generating unit of FIG.
3 is a diagram showing a waveform of a first signal output from the first light receiving unit.
4A and 4B are diagrams for explaining the operation of the differential portion of FIG.
5 is a view for explaining the magnitude of amplification of avalanche according to gate signals applied to first and second light receiving portions having different breakdown voltages.
6 is a characteristic curve showing a change in the breakdown voltage according to the thickness of the amplification layer of the Avalanche photodiode.
FIG. 7A is a view showing a cross-sectional structure of the light-receiving portion of FIG. 1 of the present invention. FIG.
7B is a plan view of the first amplification layer and the second amplification layer when the light receiving portion is viewed in the direction of the arrow shown in Fig. 7A.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Thus, in some embodiments, well known process steps, well known device structures, and well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention. Like reference numerals refer to like elements throughout the specification.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. It will be understood that when an element such as a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the element directly over another element, Conversely, when a part is "directly over" another part, it means that there is no other part in the middle. Also, when a portion of a layer, film, region, plate, or the like is referred to as being "below " another portion, it includes not only a case where it is" directly underneath "another portion but also another portion in between. Conversely, when a part is "directly underneath" another part, it means that there is no other part in the middle.

The terms spatially relative, "below", "beneath", "lower", "above", "upper" May be used to readily describe a device or a relationship of components to other devices or components. Spatially relative terms should be understood to include, in addition to the orientation shown in the drawings, terms that include different orientations of the device during use or operation. For example, when inverting an element shown in the figures, an element described as "below" or "beneath" of another element may be placed "above" another element. Thus, the exemplary term "below" can include both downward and upward directions. The elements can also be oriented in different directions, so that spatially relative terms can be interpreted according to orientation.

In this specification, when a part is connected to another part, it includes not only a direct connection but also a case where the part is electrically connected with another part in between. Further, when a part includes an element, it does not exclude other elements unless specifically stated to the contrary, it may include other elements.

The terms first, second, third, etc. in this specification may be used to describe various components, but such components are not limited by these terms. The terms are used for the purpose of distinguishing one element from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second or third component, and similarly, the second or third component may be alternately named.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

Hereinafter, a photon detection apparatus according to the present invention will be described in detail with reference to FIGS. 1 to 7B.

1 is a diagram illustrating a photon detection apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the photon detection apparatus according to an embodiment of the present invention includes a light receiving unit (APD), a gate signal generation unit 102, and a determination unit 105.

The light receiving unit APD includes a first light receiving unit APD1 and a second light receiving unit APD2.

The first light receiving portion APD1 includes an Avalanche photodiode. For example, the first light receiving unit APD1 may be an Avalanche photodiode.

The second light receiving portion APD2 includes an Avalanche photodiode. For example, the second light receiving portion APD2 may be an Avalanche photodiode.

The first light receiving portion APD1 is connected to the second light receiving portion APD2 in parallel. For example, the cathode electrode of the first light receiving unit APD1 and the cathode electrode of the second light receiving unit APD2 are connected to the first node n1, and the anode electrode of the first light receiving unit APD1 is connected to the second node n2. And the anode electrode of the second light receiving unit APD2 is connected to the third node n3.

The first node n1 is connected to the gate signal generator 102. [

The second node n2 is connected to the resistor R1. For example, the second node n2 is connected to one terminal of the resistor R1. At this time, the other terminal of the resistor R1 is connected to the ground.

The third node n3 is connected to the resistor R2. For example, the third node n3 is connected to one terminal of the resistor R3. At this time, the other terminal of the resistor R2 is connected to the ground.

The gate signal generator 102 outputs a gate signal GS in the form of a square wave (for example, in the form of a pulse or a sine wave). The gate signal GS output from the gate signal generating section 102 is supplied to the first light receiving section APD1 and the second light receiving section APD2. In other words, the gate signal GS from the gate signal generator 102 is applied to the cathode electrode of the first light receiving unit APD1 and the cathode electrode of the second light receiving unit APD2 through the first node n1 do.

At least one of the first light receiving unit APD1 and the second light receiving unit APD2 operates in a gated Geiger mode (Geiger mode) by the gate signal GS from the gate signal generating unit 102 .

The gate signal generator 102 includes a DC voltage source 112 and a pulse generator 111. The DC voltage source 112 provides a DC voltage Vdc (e.g., a bias voltage), and the pulse generating unit 111 generates a pulse PS. The gate signal generator 102 generates a pulse PS, that is, a gate signal GS swinging on the basis of the DC voltage Vdc.

2 is a diagram showing the waveform of the gate signal GS output from the gate signal generator 102 of FIG.

The gate signal GS is maintained at the first voltage Vgh during the activation period Ta and is maintained at the second voltage Vth during the rest of the inactivation period Tna except for the activation period Ta, Vgl). In other words, the gate signal GS is maintained at the first voltage (Vgh) higher than the DC voltage during the activation period Ta and is maintained at the second voltage (Vgh) lower than the first voltage (Vgh) (Vgl).

The second voltage Vgl of the gate signal GS corresponds to the above-described direct-current voltage Vdc, i.e., the bias voltage.

V _G in Fig. 2 means the amplitude of the gate signal GS. 2 is the difference voltage (i.e., the absolute value of the difference voltage) between the breakdown voltage VB and the gate signal GS (i.e., the first voltage Vgh of the gate signal GS) (? V) means an over bias voltage.

Tg in Fig. 2 means one period of the gate signal GS.

Light (e.g., photons) from the outside (e.g., a light source) is incident on the light receiving portion APD in the above-described activation period Ta. At this time, the photon is incident on only one of the first light receiving unit APD1 and the second light receiving unit APD2. For example, the photons from the outside are incident on the first light-receiving unit APD1, and are not incident on the second light-receiving unit APD2. In this case, the first light receiving unit APD1 receiving the photon is defined as the main light receiving unit APD, and the second light receiving unit APD2 not receiving the photon can be defined as the auxiliary light receiving unit APD.

The photons from the outside can be controlled to be incident on the first light receiving section APD1 in the activation period Ta in which the gate signal GS is maintained at the first voltage Vgh.

The first voltage Vgh is larger than the breakdown voltage VB of the first light receiving portion APD1. When the first voltage Vgh is applied to the first light receiving unit APD1, the first light receiving unit APD1 operates in the Geiger mode during the activation period Ta.

The gate signal GS may have a frequency of from tens of megahertz (MHz) to several gigahertz (GHz).

When a light or a photon (for example, a single photon) is incident on the first light receiving unit APD1 of the Geiger mode and a carrier (electron-pair) is generated in the first light receiving unit APD1, (APD1) and amplified by the avalanche mechanism. For example, in the forward bias, the avalanche photodiode (i.e., the first light receiving portion APD1) is turned on at its threshold voltage (e.g., about 1.0 V) or more. On the other hand, in reverse bias, when the externally applied voltage exceeds the breakdown voltage VB, a high electric field is formed at the PN junction of the avalanche photodiode. At this time, when electrons or holes generated by the absorption of photons are injected into an amplification layer to which a high electric field is applied, avalanche impact ionization is performed, and an avalanche breakdown is generated which is amplified by current through a process of avalanche impact ionization . At this point, the reverse current rapidly increases.

The Geiger mode of the Avalanche photodiode signifies a photodetection operation that is performed under reverse bias conditions greater than the breakdown voltage. Avalanche photodiodes have low gain and linear photon detection characteristics under reverse bias conditions below breakdown voltage. That is, the avalanche photodiode produces a photocurrent proportional to the number of photons incident.

However, avalanche photodiodes lose linear photodetecting properties in Geiger mode. In Geiger mode for optical detection, the Avalanch photodiode provides a large gain instead of losing its linear characteristics.

In Geiger mode, avalanche photodiode can theoretically detect single photons and produce photocurrent (ie, Geiger current). Therefore, a relatively large photocurrent can be generated in the Geiger mode, so that a photon can be detected without a separate complicated low noise amplifier (Low Noise Amplifier).

On the other hand, the Avalanche photodiode may output the same signal as when the photon is detected even when there is no photon incident from the outside. Such a detection ratio is called a Dark Count Probability pre-gate (DCP) . The dark current of the avalanche photodiode represented by the dark factor can be divided into three types. First, the generation of electron-hole pairs by thermal excitation, the second is the current generation due to the tunnel effect in the depletion region, Is a phenomenon in which the charge generated by the previously introduced light is trapped and then compensated by the next reverse bias.

In such a single photon detection device, in particular a single photon detection device in which the avalanche photodiode is operated in the Geiger mode, some of the charge carriers created during the development of the avalanche phenomenon do not immediately disappear. Thus, the charge carriers that have not completely disappeared remain within the Avalanche photodiode, and the charge carriers remaining inside the Avalanche photodiode, without being completely eliminated, are transferred to the Avalanche photodiode And generates avalanche when applied. This phenomenon is called an after pulse noise effect. The after-pulse noise can be a main factor of the reduction of the signal-to-noise ratio in the quantum information communication, and it is preferable to reduce the probability of occurrence of the after-pulse as much as possible because it is a factor that obstructs the high-

When the first voltage (Vgh) of the gate signal (GS) is applied to the cathode electrode of the Avalanche photodiode, the Avalanche photodiode is turned on, and the signal from the anode electrode of the turned-on Avalanche photodiode Is output. This signal contains a capacitive response signal due to the inherent capacitance of the avalanche photodiode. This capacitive response signal acts as a background signal for the avalanche signal.

For example, a signal (hereinafter referred to as a first signal) output from a photodetector and a first light receiving section APD1 supplied with a first voltage Vgh is supplied with an avalanche signal and a capacitance of the first light receiving section APD1 (Hereinafter referred to as a first electrostatic capacitive response signal). On the other hand, a signal (hereinafter, referred to as a second signal) output from the second light receiving section APD2 supplied with the first voltage Vgh is supplied to a second capacitance Cp corresponding to the capacitance of the second light receiving section APD2 Response signal). That is, the second light-receiving unit APD2, which is not provided with the photon, outputs the second electrostatic capacitive response signal without outputting the avalanche signal.

3 is a diagram showing the waveform of the first signal S1 output from the first light receiving unit APD1.

As shown in Fig. 3, the first signal S1 includes an avalanche signal Av and a first capacitive response signal Cp1.

On the other hand, although not shown, the second signal from the second light receiving portion APD2 includes the second electrostatic capacitive response signal. That is, as described above, since no photon is input to the second light-receiving unit APD2, when the first gate signal GS is applied to the second light-receiving unit APD2, the second light-receiving unit APD2 is connected to the second light- APD2) to output the electrostatic capacitive response signal due to the inherent electrostatic capacity.

The digital value of the avalanche signal is determined based on the threshold value (Vth). For example, as shown in Fig. 3, when the avalanche signal Av1 is less than or equal to the threshold value Vth, the digital value of the avalanche signal is determined to be zero. On the other hand, as shown in Fig. 3, when the avalanche signal Av2 is larger than the threshold value Vth, the digital value of the avalanche signal Av2 is determined to be 1. It is judged that the photon is incident on the first light receiving unit APD1 when the digital value of the Avalanche signal Av2 is determined as 1. [

The smaller the threshold value (Vth), the smaller the amplitude of the avalanche signal can be detected. However, when the threshold value Vth is smaller than the first electrostatic capacitive response signal Cp1, a digital value of 1 can be calculated by the first electrostatic capacitive response signal Cp1. In other words, although the photon is not incident on the first light-receiving unit APD1, a digital value of 1 can be calculated. In order to prevent such a malfunction, the threshold value Vth must be at least larger than the first electrostatic capacitive response signal Cp1. However, in order to increase the threshold value Vth, the amplification degree of the first light receiving section APD1 must be increased, and if the amplification degree of the first light receiving section APD1 is increased, the above-described after-pulse noise increases.

The first light receiving portion APD1 and the second light receiving portion APD2 have substantially the same electrostatic capacitive response characteristic. In other words, the first capacitive response signal Cp1 is substantially the same as the second capacitive response signal. For example, the second electrostatic capacitive response signal may be the same as the first electrostatic capacitive response signal Cp1 of FIG.

The determination unit 105 determines whether or not the first signal (i.e., the avalanche signal Av and the first electrostatic capacitive response signal Cp1) from the first light receiving unit APD1 and the second signal from the second light receiving unit APD2 And determines whether the photon is received based on the signal (i.e., the second electrostatic capacitive response signal). The determination unit 105 may include a differential unit 103 and a determination unit 104.

The differential section 103 receives the first signal output from the anode electrode of the first light receiving section APD1 and the second signal output from the anode electrode of the second light receiving section APD2 and outputs the first signal and the second signal And outputs the difference value.

The operation of the differential portion 103 will be described with reference to Figs. 4A and 4B.

Figs. 4A and 4B are diagrams for explaining the operation of the differential portion 103 of Fig. 1. Fig.

As shown in Fig. 4A, the differential section 103 inverts the phase of the second signal S2 by 180 degrees, and synthesizes the phase-inverted second signal S2 and the first signal S1.

As described above, since the first electrostatic capacitive response signal Cp1 and the second electrostatic capacitive response signal Cp2 have substantially the same magnitude, the first signal S1 and the phase-inverted second signal S2 Is synthesized, only the avalanche signal Av of the first signal S1 is detected. That is, since the second electrostatic capacitive response signal Cp2 of the inverted second signal S2 has a polarity opposite to the first electrostatic capacitive response signal Cp1, the second electrostatic capacitive response signal Cp2 has the same magnitude The sum of the first electrostatic capacitive response signal Cp1 and the second electrostatic capacitive response signal Cp2 is substantially zero. 4B, the signal generated by the combination of the first signal S1 and the phase-inverted second signal S2 (i.e., the output signal of the differential section 103) (Av).

As described above, since the light source detecting apparatus of the present invention can remove the capacitive response signal, which is a background signal, it exhibits a relatively high light detection efficiency even under a low bias condition. In addition, since the size of the gate signal GS can be lowered, noise due to the after-pulse noise effect can be significantly reduced.

The first light-receiving unit APD1 and the second light-receiving unit APD2 may be located on different substrates. For example, the first light receiving portion APD1 may be located on the first substrate, and the second light receiving portion APD2 may be located on the second substrate different from the first substrate.

A component including the first light receiving portion APD1 and the first substrate may be defined as a first module and a component including the second light receiving portion APD2 and the second substrate may be defined as a second module. When the first light-receiving unit APD1 and the second light-receiving unit APD2 are independently positioned in different modules, the device characteristics of the first light-receiving unit APD1 and the second light-receiving unit APD2 may be different from each other . The element characteristics of the first light-receiving section APD1 and the element characteristics of the second light-receiving section APD2 can be kept the same by tuning.

On the other hand, as another embodiment, the above-described first light-receiving unit APD1 and second light-receiving unit APD2 may be located on the same single substrate. For example, both the first light-receiving unit APD1 and the second light-receiving unit APD2 may be located on the substrate. The first light receiving unit APD1, the second light receiving unit APD2, and the substrate may be included in one module. When the first light-receiving unit APD1 and the second light-receiving unit APD2 are located in the same module, the device characteristics of the first light-receiving unit APD1 and the second light-receiving unit APD2 are substantially the same.

Meanwhile, as another embodiment, the first light receiving unit APD1 and the second light receiving unit APD2 may be integrated in a hybrid manner on a patterned submount. When the first light receiving unit APD1 and the second light receiving unit APD2 are manufactured in a hybrid manner, productivity can be increased due to easy module assembly.

The first light receiving unit APD1 and the second light receiving unit APD2 may have different breakdown voltages. For example, the breakdown voltage of the second light-receiving section APD2 may be larger than the breakdown voltage of the first light-receiving section APD1. In other words, the second light-receiving unit APD2 to which the photon is incident can have a larger breakdown voltage than the first light-receiving unit APD1 where no photon is incident. As an example, the breakdown voltage of the second light-receiving section APD2 is 0.1 V to 10 V greater than the breakdown voltage of the first light-receiving section APD1.

The gate signal GS of the same magnitude is applied to the first light receiving unit APD1 and the second light receiving unit APD2 under the condition that the breakdown voltage of the second light receiving unit APD2 is larger than the breakdown voltage of the first light receiving unit APD1 Only the first light receiving unit APD1 among the two light receiving units APD1 is selectively operated in the Gager mode. In other words, when the breakdown voltage of the second light receiving unit APD2 is larger than the breakdown voltage of the first light receiving unit APD1, the first light receiving unit APD1 operates in the Gager mode with respect to the gate signal GS of the same size On the other hand, the second light receiving unit APD2 does not operate in the Geiger mode.

At this time, the gate signal GS applied to the first light receiving unit APD1 and the second light receiving unit APD2 may be larger than the breakdown voltage of the first light receiving unit APD1 and the breakdown voltage of the second light receiving unit APD2. The gate signal GS applied to the first light receiving unit APD1 and the second light receiving unit APD2 is greater than the breakdown voltage of the first light receiving unit APD1 and is higher than the breakdown voltage of the second light receiving unit APD2 Can be smaller. This will be described in detail with reference to FIG.

5 is a diagram for explaining the magnitude of amplification of avalanche according to the gate signal GS applied to the first light receiving unit APD1 and the second light receiving unit APD2 having different breakdown voltages.

The first voltage Vgh of the gate signal GS is larger than VB1 and VB2 when the breakdown voltage of the first light receiving portion APD1 is VB1 and the breakdown voltage of the second light receiving portion APD2 is VB2. Since VB2 is larger than VB1 at this time, the difference voltage? V1 (i.e., the absolute value of the difference voltage) between VB1 and the first voltage Vgh of the gate signal GS is sufficiently large while VB2 and the gate signal GS (I.e., the absolute value of the difference voltage) between the first voltages (Vgh) of the first voltage Therefore, the avalanche amplification of the first light receiving portion APD1 is considerably large, while the amplification of the avalanche of the second light receiving portion APD2 is considerably small. In other words, since the first light receiving unit APD1 operates in the Geiger mode and its avalanche amplification is large, the second light receiving unit APD2 operates in a reverse bias state smaller than the reverse bias state in the Geiger mode, The amplification of the avalanche of the light receiving portion (APD2) is small. That is, the avalanche amplification of the second light receiving unit APD2 is significantly smaller than the avalanche amplification of the first light receiving unit APD1 operating in the Geiger mode.

Since the avalanche amplification of the second light receiving unit APD2 is small in this way, the probability of occurrence of the dark coefficient of the second light receiving unit APD2 decreases. As the probability of occurrence of the darkness of the second light-receiving section APD2 decreases, the noise pulse from the second light-receiving section APD2 decreases. The noise pulses from the second light receiving unit APD2 can affect the output of the first light receiving unit APD1 and thus the noise pulses from the second light receiving unit APD2 are reduced when the noise pulses of the first light receiving unit APD1 The reliability can be improved.

When the noise pulse of the second light receiving section APD2 is reduced, the output of the second light receiving section APD2 by the gate signal GS becomes a form closer to the electrostatic capacitive response signal inherent to the second light receiving section APD2 Lt; / RTI > In other words, as the noise pulse of the second light-receiving section APD2 decreases, a more accurate magnitude and type of the capacitive response signal can be detected from the second light-receiving section APD2.

On the other hand, when the breakdown voltage of the first light receiving unit APD1 is VB1 and the breakdown voltage of the second light receiving unit APD2 is VB2 ', the first voltage Vgh of the gate signal GS is greater than VB1, small. In other words, V2B 'is larger than the first voltage (Vgh) of the gate signal GS. Therefore, the first light receiving unit APD1 operates in the Geiger mode, while the second light receiver APD2 does not operate in the Geiger mode.

6 is a characteristic curve showing a change in the breakdown voltage according to the thickness of the amplification layer of the Avalanche photodiode.

In the characteristic curve of FIG. 6, the X-axis represents the thickness of the amplification layer of the Avalanche photodiode, and the Y-axis represents the breakdown voltage of the Avalanche photodiode.

As shown in Fig. 6, when the thickness of the amplification layer of the avalanche photodiode is located in the first region A1, the breakdown voltage of the avalanche photodiode is inversely proportional to the thickness of the amplification layer. In other words, the breakdown voltage of the Avalanche photodiode in the first region A1 of the characteristic curve is inversely proportional to the thickness of the amplification layer. Therefore, as the thickness of the amplification layer in the first region Al increases, the breakdown voltage decreases.

On the other hand, when the thickness of the amplification layer of the avalanche photodiode is located in the second region (A2), the breakdown voltage of the avalanche photodiode is proportional to the thickness of the amplification layer. In other words, the breakdown voltage of the avalanche photodiode in the second region A2 of the characteristic curve is proportional to the thickness of the amplification layer. Therefore, as the thickness of the amplification layer in the second region A2 increases, the breakdown voltage increases.

In general, the avalanche photodiode used for single photon detection has a good property that the thickness of the amplification layer should be located in the second region (A2). Therefore, the first area A1 is excluded from consideration.

In FIG. 6, Tm1 and Tm2 denote the thicknesses of the amplification layers of two different avalanche photodiodes, and these Tm1 and Tm2 are located in the second region A2 of the characteristic curve. For example, Tm1 corresponds to the thickness of the amplification layer of the first light-receiving section APD1, and Tm2 corresponds to the thickness of the amplification layer of the second light-receiving section APD2 described above.

In Fig. 6, VB1 represents the breakdown voltage corresponding to Tm1, and VB2 represents the breakdown voltage corresponding to Tm2. For example, VB1 corresponds to the breakdown voltage of the first light-receiving section APD1 and VB2 corresponds to the breakdown voltage of the second light-receiving section APD2.

Thus, the magnitude of the breakdown voltage of the Avalanche photodiode can be controlled by the thickness of the amplification layer contained in the Avalanche photodiode. For example, as shown in FIG. 5, both the thickness of the amplification layer of the first light receiving section APD1 and the thickness of the amplification layer of the second light receiving section APD2 are both adjusted in the second region A2 of the characteristic curve The second light receiving portion APD2 may have a larger breakdown voltage than the first light receiving portion APD1 when the second light receiving portion APD2 has an amplification layer having a greater thickness than the first light receiving portion APD1.

7A is a cross-sectional view of the light receiving portion APD of FIG. 1 according to the present invention. FIG. 7B is a cross-sectional view of the first amplification layer 707a and the second amplification layer 707b when the light receiving portion APD is viewed in the arrow direction shown in FIG. 2 amplification layer 707b.

7A and 7B, the light receiving portion APD includes a substrate 700, a conducting layer 701a, a second conductive layer 701b, a first light absorbing layer 702a, A second light-absorbing layer 702b, a first grading layer 703a, a second grading layer 703b, a first electric field control layer 704a, a second electric field control layer 704b, A first window layer 705a, a second window layer 705b, a first anode electrode 709a, a second anode electrode 709b, a first cathode electrode 710a, a second cathode electrode 710b An insulating film 715, a blocking film 800, and an anti-reflection layer 900.

The substrate 700 has a first region A1 and a second region A2 defined by the element isolation trenches 750. [ The device isolation trenches 750 may be located between two opposing sides 11, 22 of the substrate 700. Let the sides (11, 22) of the substrate (700) facing each other be defined as the first side (11) and the second side (22), respectively. The first side 11 and the second side 22 face each other in the x-axis direction. The first region AA1 is located between the element isolation trenches 750 and the first side 11 and the second region AA2 is located between the element isolation trenches 750 and the second side 22.

Although not shown, the light receiving portion (APD) of the present invention may further include an element isolation film embedded in the element isolation trench 750. The device isolation film may include an insulating material.

The substrate 700 may be a substrate including n-type InP (Indium Phosphide). In addition, the substrate 700 may be a semi-insulating substrate including InP.

The first light receiving portion APD1 is located in the first area AA1 of the substrate 700 and the second light receiving portion APD2 is located in the second area AA2 of the substrate 700. [

The first light receiving portion APD1 includes a first conductive layer 701a, a first light absorbing layer 702a, a first grading layer 703a, a first electric field adjusting layer 704a, a first window layer 705a, And includes an anode electrode 709a and a first cathode electrode 710a. Here, the first window layer 705a includes a first active region 706a, a first amplification layer 707a, and a first guard ring 708a.

The second light receiving portion APD2 includes a second conductive layer 701b, a second light absorbing layer 702b, a second grading layer 703b, a second electric field adjusting layer 704b, a second window layer 705b, And includes an anode electrode 709b and a second cathode electrode 710b. Here, the second window layer 705b includes a second active region 706b, a second amplification layer 707b, and a second guard ring 708b.

The first conductive layer 701a and the second conductive layer 701b are located on the substrate 700. [ For example, the first conductive layer 701a is located in the first area AA1 of the substrate 700 and the second conductive layer 701b is located in the second area AA2 of the substrate 700. [ Specifically, the first conductive layer 701a is located between the first region AA1 of the substrate 700 and the first light absorbing layer 702a, and the second conductive layer 701b is located between the first region AA1 of the substrate 700 and the second And is located between the region AA2 and the second light absorbing layer 702b.

The first conductive layer 701a and the second conductive layer 701b may be conductive layers each containing n-type InP.

The first and second light absorbing layers 702a and 702b convert a photon provided from the outside into a carrier, for example, electrons.

The first light absorbing layer 702a is located on the first conductive layer 701a and the second light absorbing layer 702b is located on the second conductive layer 701b. Specifically, the first light absorbing layer 702a is located between the first conductive layer 701a and the first grading layer 703a, the second light absorbing layer 702b is positioned between the second conductive layer 701b and the second grading layer 703a, Layer 703b.

The first light absorbing layer 702a and the second light absorbing layer 702b may each be a light absorbing layer containing InGaAs (Indium Gallium Arsenide). Alternatively, the first light absorbing layer 702a and the second light absorbing layer 702b may each be a light absorbing layer containing InGaAsP (Indium Gallium Arsenide Phosphide).

The first and second grading layers 703a and 703b are formed such that the carriers from the first and second light absorbing layers 702a and 702b can be transmitted to the first and second amplifying layers 707a and 707b A material having an energy band gap between the energy band gap of the light absorbing layers 702a and 702b and the energy band gap of the electric field adjusting layers 704a and 704b.

The first grading layer 703a is located on the first light absorbing layer 702a and the second grading layer 703b is located on the second light absorbing layer 702b. Specifically, the first grading layer 703a is located between the first light absorbing layer 702a and the first electric field adjusting layer 704a, the second grading layer 703b is located between the second light absorbing layer 702b and the second And the electric field adjusting layer 704b.

The first grading layer 703a may comprise a plurality of layers vertically stacked along the y-axis.

The second grading layer 703b may comprise a plurality of layers vertically stacked along the y-axis.

The first grading layer 703a and the second grading layer 703b may be grading layers each including a plurality of InGaAsP.

The first electric field control layer 704a controls the electric field of the first amplification layer 707a and the second electric field adjustment layer 704b controls the electric field of the second amplification layer 707b.

The first electric field adjusting layer 704a is located on the first grading layer 703a and the second electric field adjusting layer 704b is located on the second grading layer 703b. Specifically, the first electric field adjusting layer 704a is located between the first grading layer 703a and the first window layer 705a, the second electric field adjusting layer 704b is located between the second grading layer 703b and the first window layer 705b, 2 window layer 705b.

The first electric field adjusting layer 704a and the second electric field adjusting layer 704b may be an electric field adjusting layer including n-type InP.

The first amplification layer 707a and the second amplification layer 707b amplify the electric charge transferred from the first light absorption layer 702a and the second light absorption layer 702b.

The first amplification layer 707a is located on the first electric field adjustment layer 704a and the second amplification layer 707b is located on the second electric field adjustment layer 704b. Specifically, the first amplification layer 707a is located between the first electric field adjustment layer 704a and the first active region 706a, the second amplification layer 707b is between the second electric field adjustment layer 704b and the second amplification layer 707b, 2 active region 706b.

As shown in FIG. 7A, the thickness Tm2 of the second amplification layer 707b is larger than the thickness Tm1 of the first amplification layer 707a.

7B, the first amplification layer 707a and the second amplification layer 707b may each have a circular shape. In this case, the diameter d2 of the second amplification layer 707b May be larger than the diameter d1 of the first amplification layer 707a. Meanwhile, the first and second amplification layers 707a and 707b may have different shapes in addition to the original shape. For example, the first amplification layer 707a and the second amplification layer 707b may each have an elliptic shape.

The thickness of the first amplification layer 707a can be controlled by controlling the diffusion depth of the first active region 706a or the depth of ion implantation into the first active region 706a or by controlling the thickness of the epitaxial layer Lt; / RTI >

The thickness of the second amplification layer 707b can be controlled by controlling the diffusion depth of the second active region 706b or the depth of ion implantation into the second active region 706b or by controlling the thickness of the epitaxial layer Lt; / RTI >

If the diffusion depth of the first active region 706a and the depth of the second active region 706b are different, the thickness of the first amplification layer 707a and the thickness of the second amplification layer 707b are different. For example, when the depth of the second active region 706b is smaller than the depth of the first active region 706a, the thickness of the second amplification layer 707b is greater than the thickness of the first amplification layer 707a.

In order to minimize the deviation between the first electrostatic capacitive response signal Cp1 of the first light receiving portion APD1 and the second electrostatic capacitive response signal Cp2 of the second light receiving portion APD2, the first electric field adjusting layer 704a, (Hereinafter referred to as a first interval) between the first electric field adjusting layer 704a and the first active region 706a and the interval between the second electric field adjusting layer 704b and the second active region 706b . However, as described above, when the thickness Tm2 of the second amplification layer 707b is larger than the thickness Tm1 of the first amplification layer 707a, the second gap becomes larger than the first gap. Accordingly, the electrostatic capacitance of the second light receiving unit APD2 is reduced, and the deviation between the first electrostatic capacitive response signal Cp1 and the second electrostatic capacitive response signal Cp2 can be increased.

On the other hand, when the diameter d2 of the second amplification layer 707b increases, the capacitance of the second light receiving portion APD2 described above may increase. Therefore, if the diameter d2 of the second amplification layer 707b is increased in accordance with the change of the thickness Tm2 of the second amplification layer 707b, the second gap is larger than the first gap, The electrostatic capacitance of the first light receiving portion APD2 and the electrostatic capacitance of the first light receiving portion APD1 can be maintained substantially equal. As a result, when the thickness Tm2 and the diameter d2 of the second amplification layer 707b are greater than the thickness Tm1 and the diameter d2 of the first amplification layer 707a, the second electrostatic capacitive response signal Cp2 may have substantially the same magnitude as the first capacitive response signal Cp1.

The first amplification layer 707a and the second amplification layer 707b may each be an amplification layer containing n-type InP.

The first active region 706a is located on the first amplification layer 707a and the second active region 706b is located on the second amplification layer 707b.

The first active region 706a and the second active region 706b may each be an active region containing p-type InP.

The first guard ring 708a reduces the peak of the electric field in which the electric field is concentrated on the outer periphery of the first active region 706a while the second guard ring 708b reduces the electric field concentrated on the outer periphery of the second active region 706b Thereby reducing the peak of the electric field.

The first guard ring 708a surrounds the first active region 706a. To this end, the first guard ring 708a may have a closed curve or ring shape surrounding the first active area 706a.

A second guard ring 708b surrounds the second active region 706b. To this end, the second guard ring 708b may have a closed curve or ring shape surrounding the second active area 706b.

The insulating film 715 is located on the first window layer 705a, the second window layer 705b, and the element isolation trenches 750.

The insulating film 715 has via holes exposing portions of the first active region 706a, the second active region 706b, the first window layer 705a, and the second window layer 705b.

The first anode electrode 709a is connected to the first active region 706a through a via hole exposing the first active region 706a and the second anode electrode 709b is connected to the second active region 706b through the via hole exposing the first active region 706a, And is connected to the second active region 706b via a via hole.

The first cathode electrode 710a is connected to the first window layer 705a via a via hole exposing the first window layer 705a and the second cathode electrode 710b is connected to the second window layer 705b through a via hole exposing the first window layer 705a, And is connected to the second window layer 705b via a via hole.

Two opposed faces 10 and 20 of the substrate 700 are defined as a first face 10 and a second face 20, respectively. The first surface 10 and the second surface 20 face each other in the y-axis direction. The first conductive layer 701a and the second conductive layer 701b described above are located on the first side 10 of the substrate. The blocking layer 800 is then positioned on the second side 20 of the substrate 700. At this time, the blocking layer 800 has a transmission hole 850 corresponding to the first amplification layer 707a. In other words, the blocking film 800 has a through hole 850 located corresponding to the first area AA1.

The blocking layer 800 overlaps the second amplification layer 707b. The second region AA2 of the substrate 700 is located between the blocking layer 800 and the second amplification layer 707b.

Due to this blocking film 800, light or photons from the outside can be incident only on the first light-receiving part APD1 of the first light-receiving part APD1 and the second light-receiving part APD2.

The anti-reflection film 900 is located in the transmission hole 850. Light or photons from the outside are provided to the first light receiving section APD1 through the antireflection film 900 in the transmission hole 850. [

The light receiving portion APD of the present invention includes an ohmic contact layer 731a, a first cathode electrode 710a, and a first window layer 705a disposed between the first anode electrode 709a and the first active region 706a. An ohmic contact layer 731b and a second cathode layer 710b located between the second anode 709b and the second active region 706b and a second window layer 705b, And an ohmic contact layer 732b located between the ohmic contact layers 732a and 732b.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. Will be clear to those who have knowledge of.

102: Gate signal generator 105:
APD: light receiving part APD1: first light receiving part
APD2: second light receiving section 103:
104: discrimination part GS: gate signal
n1: first node n2: second node
Vdc: DC voltage PS: Pulse
111: Pulse generator 112: DC voltage source
R: Resistance

Claims (14)

A first light receiving unit receiving a gate signal and outputting a first signal;
A second light receiving unit receiving the gate signal and outputting a second signal; And
And a determination unit for determining whether a photon is received based on a first signal from the first light receiving unit and a second signal from the second light receiving unit;
A photon is incident on the first light receiving portion of the first light receiving portion and the second light receiving portion;
Wherein the breakdown voltage of the second light receiving portion is larger than the breakdown voltage of the first light receiving portion. The method according to claim 1,
Wherein the breakdown voltage of the second light receiving section is 0.1 V to 10 V larger than the breakdown voltage of the first light receiving section The method according to claim 1,
Wherein the amplification layer of the first light receiving section and the amplification layer of the second light receiving section have different thicknesses. The method of claim 3,
Wherein the amplification layer of the second light receiving portion has a greater thickness than the amplification layer of the first light receiving portion. 5. The method of claim 4,
Wherein the amplification layer of the second light receiving portion has a thickness that is 5% to 50% greater than the amplification layer of the first light receiving portion. The method according to claim 1,
Wherein the amplification layer of the first light receiving section and the amplification layer of the second light receiving section have different diameters. The method according to claim 6,
Wherein the amplification layer of the second light receiving portion has a larger diameter than the amplification layer of the first light receiving portion. The method according to claim 1,
Wherein the first light receiving portion and the second light receiving portion are formed on the same substrate. 9. The method of claim 8,
And the first light receiving portion and the second light receiving portion are located on the first surface of the substrate. 10. The method of claim 9,
And a blocking film located on a second side of the substrate facing the first side of the substrate. 11. The method of claim 10,
Wherein the blocking film has a through hole located corresponding to the first light receiving portion. 12. The method of claim 11,
And an anti-reflection film positioned in the through hole. 10. The method of claim 9,
Wherein the first surface of the substrate includes a first region and a second region separated by an element isolation groove between the first light receiving portion and the second light receiving portion;
The first light receiving portion is located in the first region, and the second light receiving portion is located in the second region. The method according to claim 1,
Wherein the electrostatic capacitive response characteristic of the first light receiving portion by the gate signal is substantially equal to the electrostatic capacitive response characteristic of the second light receiving portion by the gate signal.

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